Imagine a mobile device without the need to recharge ever. BBC News has a report on the work of Assistant Professor Marin Soljacic and his colleagues Aristeidis Karalis and John Joannopoulos about wireless power transfer.
The system is consisted of two antennas - one on the power source, the other on the device - resonating at 6.4MHz. The electromagnetic waves (energy) picked up by the device is used to recharge the battery. Resonance is a natural phenomena visibly observed in musical instruments.
In physics, resonance is the tendency of a system to oscillate when excited by energy at a certain frequency. This frequency is known as the system’s natural frequency of vibration, resonant frequency, or eigenfrequency. A resonant object, whether mechanical, acoustic, or electrical, will be easy to vibrate at resonant frequency, and more difficult to vibrate at other frequencies.